No Solder Slim PS2 Mod Problem

I recently purchased the no solder mod for my slim PS2. I have used the slide card with my orignal PS2 and it played all the backups just fine. My problem is this...my slimline PS2 will not read my backups. It always says "Invalid PS2 Disc" when i boot up swap magic 3.3 They played fine in the other PS2. Any ideas on whats wrong? Thanks in advance